To trace family in Poland, you need to know their town of birth. It is also best to know parents' names, including maiden surname of mother. If this information is not on Tadeusz's death record, you can obtain his ss application, which should have this information on it.
Social Security Administration OEO FOIA Workgroup 300 N. Green Street P.O. Box 33022 Baltimore, Maryland 21290-3022
It's $27 with SS# & $29 without. If you need it, let me know.